JP3242763B2 - Video synthesis method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a collaborative drawing space in which users dispersed in remote places can simultaneously point and draw by synthesizing and sharing images on their desks. The present invention relates to a method and apparatus for synthesizing an image in a video communication terminal device that enables collaborative work by groups such as design work and software development on their own desks.

[0002]

2. Description of the Related Art Conventionally, image input means for inputting an image,
A communication interface for transmitting and receiving video, video synthesizing means for superimposing a plurality of input video images so that the video images can be seen through each other, and video output means for outputting the superimposed video to a display device or a communication line; There is a video communication terminal that provides a cooperative drawing space by transmitting and receiving a video image of a desktop and combining and displaying it in a semi-transparent shape (Japanese Patent Application No. 2-238627). FIG. 11 shows a configuration example of a system using the conventional terminal. In FIG. 11, 101
And 105 are conventional terminals, and 109 is a communication line connecting these terminals. Each terminal 101, 10
In 5, reference numerals 104 and 108 denote video cameras for photographing respective desktop images, 103 and 107 denote translucent composition devices for translucent composition so that the images can be seen through each other, and 102 and 106 denote display devices.

[0005] As shown in FIG. 12, the conventional terminal displays a video 201 (photographed by the video camera 104) of the desktop of itself and a video 202 (photographed by the video camera 108) of the desk of the other party. By combining them in a semi-transparent shape so that they can be seen through, a cooperative drawing space in which both can simultaneously write, as shown in the video 203 (displayed on the display devices 102 and 106), is realized. .

[0004] A video composing method (implemented in 103 and 107) in the conventional terminal will be described below. When an image V ₁ and V ₂ of X × Y pixels are combined at an arbitrary ratio to generate an image V, coordinates (x, y) (1 ≦ 1) of each image V ₁ , V ₂ , V
x ≦ X, 1 ≦ y ≦ Y, x and y V respectively in pixels natural _number) 1xy, V _2xy, and V _xy. Assuming that the synthesis ratio of V ₁ and V ₂ is w ₁ : w ₂ (w ₁ + w ₂ = 1, w ₁ ≧ 0, w ₂ ≧ 0), the following expression is used for all coordinates (x, y). Perform synthesis.

V _xy = w ₁ V _1xy + w ₂ V _2xy (1) A flow chart of a conventional video synthesizing method is shown in FIG. That is, starting from y = 1, x = 1,
The composition is performed by the equation (1), and the composition by the equation (1) is repeated until the x coordinate is increased by 1 and x> X. Next, when x> X, the y coordinate is incremented by one, and the synthesis process from x = 1 to x = X is repeated until y> Y.

FIG. 14 schematically shows translucent synthesis using the conventional method. Image 401 and 402 are combined at a ratio of 0.5:
When synthesized at 0.5, as shown in the image 403, a pixel obtained by synthesizing a white pixel and a black pixel (a white pixel is 1 and a black pixel is 0) is a gray (0.5) pixel.

[0007]

For this reason, when both desk-top images are combined by the image combining method according to the above-mentioned conventional technique, the contrast of both drawings decreases as shown in FIG. There is a problem that drawing becomes difficult to see. Also, the method of connecting two points and synthesizing two images has been described as an example. However, when the number of images to be synthesized increases, the contrast further decreases. It has been difficult to realize a video communication system for synthesizing video.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to combine a plurality of images taken on a desk in a semi-transparent manner so that they can be seen through each other. In a video communication terminal that realizes a cooperative drawing space in which a user can point and draw at the same time, in particular, it solves the inconsistency caused by a decrease in contrast that occurs when a large number of videos are combined in a semi-transparent shape. And a video synthesizing method and apparatus for realizing a video communication terminal capable of providing a cooperative drawing space by connecting the video communication terminals.

[0009]

To achieve the above object, according to an aspect of, the image synthesis method according to claim 1 of the present invention, N is the plurality of video V ₁ as a natural number greater than, ..., V _N mutual video a video synthesizing method for synthesizing an arbitrary ratio so that seen through the video V _1, ..., the threshold S ₁ of luminance corresponding independently to V _N, ..., the first to set a S _N phase and the video V _1, ..., the V _N, certain coordinate x included in the region R for synthesizing the pixels _y V 1xy, ..., V
_Nxy, respectively I _V1xy the luminance of the pixel, ..., comparing the second stage of the I _VNxy, for 1 ≦ n ≦ N all natural number n is, the luminance I _Vnxy as defined above threshold S _n The third step, and the luminance I _Vnxy for all n
Is brighter or darker than the threshold value S _n , the sum of pixels V _nxy for all n at a set ratio is set as a synthesized pixel at coordinates x and y,
In other cases anda fourth step of the synthesis pixels obtained by adding synthesized in the proportions set only pixels having luminance darker than the threshold S _n coordinates x, in y, the third The step and the fourth step are applied to all coordinates x and y included in the region R.

Also, in order to achieve the above object,
A video synthesizing apparatus according to a second aspect of the present invention is a video synthesizing apparatus that executes the video synthesizing method according to the first aspect, wherein N is 1
A plurality of video V ₁ as a natural number greater than, ..., the image synthesizing apparatus for synthesizing an arbitrary ratio so that V _N seen through each other's image, the image V _1, ..., was set V _N respective luminance signals A luminance signal comparing means for comparing with a threshold signal, and a control based on the comparison result from the luminance signal comparing means, adds and synthesizes an arbitrary number of images of the plurality of images in a translucent manner at an arbitrary ratio. Translucent synthesizing means, and means for switching between the respective images or the images added and synthesized by the translucent synthesizing means and outputting as a synthesized image by control based on the comparison result from the luminance signal comparing means. Configuration.

Also, in order to achieve the above object,
In the video synthesizing method according to claim 3 of the present invention, N is a natural number larger than ₁ , and the plurality of videos V ₁ ,..., V _N are synthesized at an arbitrary ratio so that the images can be seen through each other. With respect to the images V ₁ ,..., V _N , pixels at certain coordinates x, y included in the region R to be synthesized are _represented by V _1xy,.
V _{N xy,} respectively the luminance of the pixels I _V1xy, ..., I _VNxy
A second step of comparing the luminances I _{Vnxy with} each other for all n (1 ≦ n ≦ N, where n is a natural number), and a pixel having the darkest luminance at a coordinate x, y And wherein the second and third steps are applied to all coordinates x and y included in the region R.

Further, in order to achieve the above object, a video synthesizing apparatus according to claim 4 of the present invention is a video synthesizing apparatus for executing the video synthesizing method according to claim 3, wherein
A plurality of video V ₁ was a 1 a natural number greater than, ..., the image synthesizing apparatus for synthesizing an arbitrary ratio so that V _N seen through each other's image, the image V _1, ..., a V _N respective luminance signals A luminance signal comparing unit to be compared and a unit for switching each of the images and outputting as a composite image by control based on the comparison result from the luminance signal comparing unit are provided.

[0013]

In the image synthesizing method and apparatus of the present invention, when synthesizing a plurality of images so that the images can be seen through each other, a large number of images are changed by changing the synthesizing method for each pixel according to the luminance of the pixel of each image. Is prevented from lowering when the image is synthesized in a semi-transparent manner, and the inconsistency due to the lowering of the contrast is improved.

In the video synthesizing method according to the first aspect of the present invention, a corresponding threshold value of luminance is set independently for all the images, and the luminance of a pixel at a certain coordinate is set for all the images. If the pixel is brighter or darker than the corresponding threshold, the corresponding pixels of all the images are added and synthesized at the set ratio, otherwise, only the pixels with luminance lower than the threshold are added at the set ratio. Synthesize
The contrast is prevented from lowering.

In the video synthesizing apparatus according to a second aspect of the present invention, the brightness of each video to be synthesized is compared with a corresponding threshold value by a brightness signal comparing means, and an arbitrary number of videos are optionally determined according to the comparison result. 2. The video synthesizing method according to claim 1, wherein the image to be synthesized and the synthesizing ratio are controlled by a translucent synthesizing means for synthesizing at a synthesizing ratio of each of the following, and further, each image or the synthetic image of the translucent synthesizing means is switched by a switching means. To achieve.

In the image synthesizing method according to the third aspect of the present invention, for all the images, the luminances of the corresponding pixels at certain coordinates are compared with each other, and the pixel having the darkest luminance is set as the synthesized pixel, thereby achieving a high contrast. Prevents decline.

In the video synthesizing apparatus according to a fourth aspect of the present invention, the luminance of each video is compared by the luminance signal comparing means of each video, and the output video is switched by the switching means according to the comparison result. 3 is realized.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[Embodiment 1] In this embodiment, the video synthesizing method according to claim 1 of the present invention will be specifically described using an example of synthesizing a plurality of videos.

A plurality of images V ₁ , composed of X × Y pixels,
.., V _N (N is a natural number greater than 1) respectively w ₁ :
…: W _N (however, w ₁ +... + W _N = 1, w ₁ ,..., W _N ≧
0), the image V is generated by synthesizing the image at the coordinates (x, y) (1) of the image V _n (1 ≦ n ≦ N, where n is a natural number).
The pixel in ≦ x ≦ X, 1 ≦ y ≦ Y, x and y are natural numbers) is V _nxy , and the brightness of the pixel is I _Vnxy (0 ≦ I _Vnxy ≦ 1
Where 0 indicates black and 1 indicates white). Also, the image V _n
The threshold value of the brightness corresponding to S _n (0 ≦ S _n
≤ 1).

The video V ₁ using the image synthesis method according to claim 1 of the present invention in FIG. 1, ..., a V _N w _1: ...: when generating the image V synthesized in synthesis ratio of w _N 3 shows an example of a flowchart. Coordinates (x, y) of each image V _n is 501 parts in, calculates the total of w number c and their mixing ratio of the pixels having luminance I _Vnxy above threshold S _n. At 502, it is determined whether all the pixels are below the threshold (c = 0) or above the threshold (c = N).
03 copies are executed, and if not applicable, 504 copies are executed. 5
Sections 03 and 504 are sections for performing pixel synthesis. The unit 503 adds and synthesizes the pixels V _nxy in all the images V _{n at} a ratio of w _n , and the unit 504 first sets the average value W (= w / w /
c) is calculated, and performs composition by the threshold S _n is smaller than the luminance I _Vnxy for pixels having only, v = v + (W + w n) formula V _NXY (506 and 507). And pixel v _xy of the composite pixel v video V coordinates (x, y) in 508 parts. The above-described image synthesis processing is performed with y = 1 and x = 1.
And after the execution is completed, the x coordinate is incremented by 1, and x>
The processing of the video composition is repeated until the value becomes X. Next, when x> X, the y coordinate is incremented by one, and the above-described image synthesis processing from x = 1 to x = X is repeated until y> Y.

In this embodiment, when pixels are combined, an example is shown in which the composition ratio of pixels not to be combined is averaged and distributed (W of 507 parts). It is also possible to distribute the composition ratio of non-combined pixels in proportion to the composition ratio of the pixels to be composed.

[0023] v = v + In [{w / (1-w )} w n + w n] V nxy [ Embodiment 2] This embodiment, the video synthesis method according to claim 1 of the present invention, two images This will be specifically described using an example in which is synthesized.

Two images V ₁ , composed of X × Y pixels,
The V ₂ w _1: w ₂ (where _{w 1 + w 2 = 1,} w 1 ≧ 0, w 2 ≧
When generating the image V synthesized in synthesis ratio of 0), the coordinates of the image V ₁ and _{V 2 (x, y) (} 1 ≦ x ≦ X, 1 ≦ y ≦
Y, x and y are natural numbers) are V _1xy and V _2xy , respectively, and the luminance of the pixel is I _V1xy and I _V1xy , respectively.
_V2xy (0 ≦ I _V1xy ≦ 1, 0 ≦ I _V2xy ≦ 1, where 0 indicates black and 1 indicates white). Further, the threshold values of the luminance of the images V ₁ and V ₂ are set to S ₁ and S ₂ (0 ≦ S ₁ ≦ 1, 0 ≦ S ₂ ≦
1).

In this embodiment, the pixel _Vxy at the coordinates (x, y) of the video V to be generated is given by the following equation. This is shown in the flowchart of FIG. In FIG. 2, a portion 601 is a portion that executes the following equation in different cases.

When I _V1xy <S ₁ and I _V2xy <S ₂ , V _xy = w ₁ V _1xy + w ₂
When V _2xy I _V1xy ≧ S ₁ and I _V2xy ≧ S ₂ V _xy = w ₁ V _1xy + w ₂
When V _2xy I _V1xy ≧ S ₁ , I _V2xy <S ₂ V _xy = V _2xy I _V1xy <S ₁ , When I _V2xy ≧ S ₂ V _xy = V _1xy [Third Embodiment] In this embodiment, FIG. FIG. 7 schematically shows a process of synthesizing two images according to the second embodiment. Video 701 and Video 7
02 is synthesized using the flowchart shown in FIG. 2 at a synthesis ratio of 0.5: 0.5, a synthesized image with clear contrast as shown in an image 703 is obtained. In the present embodiment, as is apparent from comparison with FIG. 14 of the conventional example, a pixel obtained by combining a white pixel and a black pixel does not become a gray pixel but becomes a black pixel, thereby preventing a decrease in contrast.

[Embodiment 4] In the present embodiment, the video synthesizing apparatus according to the second embodiment of the present invention will be specifically described with an example of a video synthesizing apparatus that performs the video synthesizing method described in the second embodiment. I do.

In FIG. 4, reference numerals 801 and 802 denote input lines for images to be synthesized, and input images V ₁ and V ₂ , respectively. 803 and 804 are input lines for threshold signals S ₁ and S ₂ , 805 is a division resistor, 806 and 807 are converters, 808 is an operational amplifier with an amplification factor of 1, 809 and 810
Is a Schmitt trigger, 811, 812 and 813 are delay lines, 814 is an analog switch, and 815 is a video output line.

In the image synthesizing apparatus shown in FIG. 4, the images V ₁ and V ₂ input from the image input lines 801 and 802 are sent to comparators 806 and 807, respectively, and the magnitudes of the luminance and threshold signals S ₁ and S ₂ are compared. Comparator 806,
The output of 807 becomes high or low, and this output is shaped through Schmitt triggers 809 and 810,
It is input to the control terminals C ₀ and C ₁ of the analog switch 814. The images V ₁ and V ₂ are sent to delay lines 811 and 812, respectively,
Are added to each other by.
08, the delay line 813
Through to the analog switch 814. The control terminals C ₀ and C ₁ of the analog switch 814 have a high level of 1 and a low level of 0. When the values of C ₁ and C ₀ are 00, the signal of the input terminal I ₀ (the output signal of the delay line 813) is output. , 01, the signal at the input terminal I ₁ (the output signal of the delay line 811) is 10, and at 10, the input terminal I ₂
Signal (the output signal of the delay line 812) is, when the 11 signal at the input terminal I ₃ (output signal of the delay line 813) is output to the video output line 815.

The delay lines 811, 812, 8
Reference numeral 13 is for adjusting the time difference between the analog input of the analog switch 814 and the control signal, and may be omitted when the video signal does not particularly require high quality.

[Embodiment 5] In this embodiment, the fourth embodiment will be described.
2 shows a configuration example of a video communication terminal and a video communication system using the video synthesizing apparatus described in.

In FIG. 5, reference numerals 901 and 905 denote the video communication terminals, and 909 denotes a communication line connecting these terminals. In each of the terminals 901, 905, 904 and 908 are video cameras for photographing respective desktop images, 903 and 907 are the video synthesizing devices according to the second embodiment of the present invention described in the fourth embodiment, and 902 and 906 are display devices. Device.

[Embodiment 6] In this embodiment, a result of synthesizing both desktop images using the video communication system shown in FIG. 5 will be described.

In FIG. 6, an image 1001 is an image of the user's desk (photographed by the video camera 904), and an image 1002 is an image of the other person's desk (video camera 9).
08), and a video 1003 is a composite video (display device 9).
02 and 906). According to this embodiment, a decrease in contrast is prevented, and a drawing or the like photographed and synthesized by oneself and the other party can be clearly seen.

[Embodiment 7] In this embodiment, the video synthesizing method according to claim 3 of the present invention will be specifically described using an example of synthesizing a plurality of videos.

A plurality of videos V ₁ ,
.., V _N (N is a natural number greater than 1) and the video V
Is generated, the image V _n (1 ≦ n ≦ N, n is a natural number)
(X, y) (1 ≦ x ≦ X, 1 ≦ y ≦ Y, x and y
Is a natural number), the pixel is V _nxy , and the brightness of the pixel is I
_Vnxy (0 ≦ I _Vnxy ≦ 1, black when 0, white when 1).

FIG. 7 shows an example of a flow chart in the case where the image V is generated by synthesizing the images V ₁ ,..., V _N using the image synthesizing method according to claim 3 of the present invention. In this embodiment, 1
In part 101, a pixel v having the lowest (dark) luminance at coordinates (x, y) is obtained, and in part 1102, 11 is obtained.
It is assumed that the darkest pixel obtained in part 01 is a pixel _Vxy to be obtained.
The above-described video synthesizing process is started from y = 1 and x = 1, and after the execution is completed, the x coordinate is incremented by 1 and the video synthesizing process is repeated until x> X. Next, when x> X, the y coordinate is incremented by one, and the above-described image synthesis processing from x = 1 to x = X is repeated until y> Y.

[Embodiment 8] In this embodiment, in the video synthesizing apparatus according to the fourth aspect of the present invention, two images V ₁ ,
It will be described in detail with reference to examples for outputting an image V by combining the V _2.

In FIG. 8 , reference numerals 1201 and 1202 denote input lines for images to be synthesized, reference numeral 1203 denotes a comparator for inputting and comparing the respective images V ₁ and V ₂ , reference numeral 1204 denotes a Schmitt trigger for shaping the output of the comparator 1203, 1205 and 1206 are delay lines, 120
7 is an analog switch. Analog switch 120
7, when the control terminal C is low, the signal of the input terminal I ₀ (the output signal of the delay line 1205)
Is high, the signal of the input terminal I ₁ (the output signal of the delay line 1206) is output to the video output line 1208.

In the video synthesizing apparatus shown in FIG.
Video V ₁ inputted from 01,1202, V ₂ is input to the comparator 1203, the relationship between each luminance value V ₁
<When V ₂ video V ₁ becomes the output of the Schmitt trigger 1204 low is output from the video output line 1208, V _1>
When V ₂ video V ₂ becomes the output of the Schmitt trigger 1204 to a high is output from the video output line 1208.

The delay lines 1205 and 1206
Is for adjusting the time difference between the analog input of the analog switch 1207 and the control signal, and may be omitted when the video signal does not particularly require high quality.

[Embodiment 9] In this embodiment, the embodiment 8 will be described.
2 shows a configuration example of a video communication terminal and a video communication system using the video synthesizing apparatus described in.

In FIG. 9, 1301 and 1305 are the video communication terminals, respectively, and 1309 is a communication line connecting these terminals. Reference numerals 1304 and 1308 denote video cameras for capturing respective desktop images, and 1303.
Reference numerals 1307 and 1307 denote image synthesizing apparatuses according to the fourth embodiment of the present invention described in the eighth embodiment, and 1302 and 1306 denote display apparatuses.

[Embodiment 10] In this embodiment, a result of synthesizing both desktop images using the video communication system shown in FIG. 9 will be described.

In FIG. 10, an image 1401 is an image obtained by photographing the user's desk (photographed by the video camera 1304).
A video 1402 is a video of the other party's desk (photographed by the video camera 1308), and a video 1403 is a composite video (displayed on the display devices 1302 and 1306). According to this embodiment as well, a decrease in contrast is prevented, and a drawing or the like photographed and synthesized by oneself and the other party can be clearly seen.

[0046]

As described above, the image synthesizing method and apparatus according to the present invention is based on the fact that the synthesizing method is changed according to the brightness of each pixel when synthesizing a plurality of images so that the images can be seen through each other. In a video communication terminal that realizes a cooperative drawing space by combining a plurality of images taken on a desk in a semi-transparent shape, the contrast of the cooperative drawing space is improved,
This has the effect of improving the visibility of documents and drawings. In addition, even when a large number of images are combined, the contrast can be similarly improved, so that a multi-point compatible cooperative drawing space that can be connected to multiple points and combined with a large number of desktop images to be shared. There are benefits that can be realized.

[Brief description of the drawings]

FIG. 1 is a flowchart for explaining an embodiment of a video synthesizing method according to claim 1 of the present invention;

FIG. 2 is a flowchart illustrating a method for synthesizing two images, in particular, an embodiment of the image synthesizing method according to claim 1 of the present invention;

FIG. 3 is a diagram schematically illustrating image synthesis by the image synthesis method according to the embodiment of FIG. 2;

FIG. 4 is a block diagram showing an embodiment of a video synthesizing apparatus according to claim 2 of the present invention, particularly a video synthesizing apparatus for synthesizing two videos.

FIG. 5 is a diagram showing a configuration example of a video communication terminal and a video communication system using the video synthesis device according to claim 2 of the present invention.

6 is a diagram showing a result of synthesizing both desk videos using the video communication system shown in FIG. 5;

FIG. 7 is a flowchart for explaining an embodiment of the video synthesizing method according to claim 3 of the present invention;

FIG. 8 is a diagram showing an example of a configuration of a video synthesizing apparatus according to an embodiment of the present invention, which particularly synthesizes two videos.

9 is a diagram showing a configuration example of a video communication terminal and a video communication system using the video synthesis device according to the embodiment of FIG. 8;

FIG. 10 is a diagram showing a result of synthesizing both desktop images using the video communication system shown in FIG. 9;

FIG. 11 is a diagram showing a configuration example of a video communication system by a terminal using a conventional video synthesis method.

FIG. 12 is a diagram showing a result of synthesizing a desk image by a conventional image synthesizing method.

FIG. 13 is a flowchart illustrating an example of a conventional video composition method.

FIG. 14 is a diagram schematically illustrating video synthesis by a conventional video synthesis method.

[Explanation of symbols]

801, 802: video input lines for inputting images to be synthesized 803, 804: threshold signal input lines for inputting set threshold values 805: split resistors for synthesizing images in a semi-transparent state 806, 807 ... comparators 808: operational amplifiers with an amplification factor of 1 809, 810: Schmitt triggers 811, 812, 813 ... delay lines 814 ... analog switches 815 ... video output lines 901, 905 ... video communication terminals using a video synthesizing device 902, 906 ... display devices 903 , 907... Video synthesizing devices 904 and 908... Video camera 909 for photographing a desktop image 909... Communication line 1001... Own desktop image photographed by the video camera 904 1002. Image 120 obtained by synthesizing image 1002 .., 1202... Video input line for inputting a video to be synthesized 1203... Comparator 1204. Schmitt trigger 1205, 1206 delay line 1207, analog switch 1208, video output line 1301, 1305. ... display devices 1303, 1307 ... video synthesizing devices 1304, 1308 ... video cameras for photographing desktop images 1309 ... communication line 1401 ... own desktop images captured by the video camera 1304 1402 ... counterpart desktop images captured by the video camera 1308 1403 … Video that combines video 1401 and video 1402

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Ishibashi 1-6-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) References JP-A 4-119087 (JP, A) 1-95875 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 5/262-5/265 H04N 7/15 G06T 3/00 300

Claims (4)

(57) [Claims] 1. A video synthesizing method for synthesizing a plurality of videos V ₁ ,..., V _N at an arbitrary ratio so that the videos can be seen through each other, where N is a natural number larger than ₁ . threshold S ₁ of luminance corresponding independently to _N, ..., a first step of setting the S _N, the video V _1, ..., the V _N, certain coordinate included in the region R for synthesizing x, the pixels of _{y V 1xy, ..., V Nxy} , respectively I _V1xy the luminance of the pixel, ..., a second step of the I _VNxy, for 1 ≦ n ≦ n all natural number n is, the luminance I a third step of comparing the a _Vnxy each of the threshold S _n, whether said luminance I _Vnxy for all n brighter than the threshold value S _n, or if dark pixel V for all n A composite image at coordinates x and y is obtained by adding and synthesizing at the set ratio of _nxy And iodine, anda fourth step of coordinates x, a composite pixel in the y those obtained by adding synthesized in the proportions set only pixels with the threshold value S luminance darker than _n in other cases, An image composition method, wherein the third and fourth steps are applied to all coordinates x and y included in the region R. 2. A video synthesizing apparatus for executing the video synthesizing method according to claim 1, wherein N is a natural number greater than ₁ and the plurality of videos V _{1 ,.}
, V _N , a luminance signal comparing unit that compares each luminance signal of the images V ₁ ,..., V _N with a set threshold signal. By the control based on the comparison result from the luminance signal comparing unit, a translucent combining unit that adds and synthesizes an arbitrary number of images in a translucent manner at an arbitrary ratio among the plurality of images, Means for switching the respective images or the images added and synthesized by the translucent synthesizing means and outputting as a synthesized image by control based on the comparison result. 3. A video synthesizing method for synthesizing a plurality of images V ₁ ,..., V _N at an arbitrary ratio so that the images can be seen through each other as N is a natural number larger than ₁ . for _n, certain coordinate x included in the region R for synthesizing the pixels _{y V 1xy, ..., V Nxy} , respectively I _V1xy the luminance of the pixel, ..., a first stage of the I _VNxy, all n (1 ≦ n ≦ N, where n is a natural number) including a second step of comparing the luminances I _{Vnxy with} each other, and a third step of setting a pixel having the darkest luminance as a composite pixel at coordinates x and y. A video synthesizing method, wherein the second and third steps are applied to all coordinates x and y included in the region R. 4. A video synthesizing apparatus for executing the video synthesizing method according to claim 3, wherein N is a natural number greater than ₁ and the plurality of videos V _{1 ,.}
, V _N, a luminance signal comparing means for comparing respective luminance signals of the images V ₁ ,..., V _N , Means for switching the respective images by a control based on a comparison result and outputting the combined images as a composite image.